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Biomedical subjects

S Zhai

Publications and source records attributed to S Zhai.

At least 19 recordsLinked to original sources

Concurrent paclitaxel and radiation in the treatment of locally advanced head and neck cancer.

PURPOSE: To determine the feasibility of an organ preservation regimen consisting of infusional paclitaxel administered concurrently with radiotherapy to patients with locally advanced head and neck squamous cell carcinoma (HNSCC). PATIENTS AND METHODS: Thirty-three previously untreated patients with stage III or IV tumors were enrolled onto the study. Paclitaxel was administered as a 120-hour continuous infusion every 3 weeks during the course of radiation therapy. Sixteen patients received a paclitaxel dose of 105 mg/m(2), and 17 patients received 120 mg/m(2). Radiation was delivered in a standard format at 1.8 Gy/d to a total dose of 70.2 to 72 Gy. RESULTS: Three months after therapy, a 76% complete response (CR) at the primary site and a 70% overall CR was achieved. At 36 months, locoregional control was 55.7%, overall survival was 57.8%, and disease-free survival was 51.1%. The median survival duration for all 33 patients was greater than 50 months at the time of this report. Local toxicities including mucositis, dysphagia, and skin reactions were severe but tolerable. All patients retained functional speech, and all but four patients were swallowing food 3 months after treatment. Steady-state plasma concentrations for paclitaxel were not achieved during a 120-hour infusion, suggesting a nonlinear process. Tumor volume quantified by pretreatment computerized tomography imaging was associated with likelihood of response and survival. CONCLUSION: Paclitaxel administered as a 120-hour continuous infusion in combination with radiotherapy is a feasible and promising treatment for patients with advanced HNSCC.

Adult↗

Impact of the putative differentiating agent sodium phenylbutyrate on myelodysplastic syndromes and acute myeloid leukemia.

Sodium phenylbutyrate (PB) is an aromatic fatty acid with cytostatic and differentiating activity against malignant myeloid cells (ID(50), 1-2 mM). Higher doses induce apoptosis. Patients with myelodysplasia (n = 11) and acute myeloid leukemia (n = 16) were treated with PB as a 7-day continuous infusion repeated every 28 days in a Phase I dose escalation study. The maximum tolerated dose was 375 mg/kg/day; higher doses led to dose-limiting reversible neurocortical toxicity. At the maximum tolerated dose, PB was extremely well tolerated, with no significant toxicities; median steady-state plasma concentration at this dose was 0.29 +/- 0.16 mM. Although no patients achieved complete or partial remission, four patients achieved hematological improvement (neutrophils in three, platelet transfusion-independence in one). Other patients developed transient increases in neutrophils or platelets and decrements in circulating blasts. Monitoring of the percentage of clonal cells using centromere fluorescence in situ hybridization over the course of PB administration showed that hematopoiesis remained clonal. Hematological response was often associated with increases in both colony-forming units-granulocyte-macrophage and leukemic colony-forming units. PB administration was also associated with increases in fetal erythrocytes. These data document the safety of continuous infusion PB and provide preliminary evidence of clinical activity in patients with myeloid malignancies.

Acute Disease↗

[The role of fibrinolysis in pathogenesis of middle ears adhesions].

OBJECTIVE: To investigate the role of fibrinolysis in pathogenesis of middle ears adhesions. METHODS: The amount of Tissue-type Plasminogen Activator (tPA) of 28 sections from 6 ears with adhesive otitis media (AOM) and of 22 sections from 6 normal ears was examined by Super Sensitive Biotin-Streptavidin (SSBSA) method. Amount of Fibrin of 11 sections from 3 ears with significant adhesions was compared with that of 12 sections from 3 normal ears. Qualitative analysis of light microscopy with computer-assisted image system was employed. RESULTS: In adhesive ears, tPA stains were negative in 11 of 28 sections and faint positive were 10 of 28 sections, while Fibrin stains were positive in 6 of 11 sections and strong positive were in 3 of 11 sections. In normal ears, tPA stains positive were in 8 of 22 sections and strong positive were 10 of 22 sections, meanwhile, fibrin stains were negative in 8 of 12 sections and faint positive were in 3 of 12 sections. Quantitative analysis showed that the amount of tPA was 16.70 +/- 5.11 and 39.84 +/- 6.26 in ears with AOM and normal ones respectively (P < 0.05). CONCLUSION: In adhesive ears the amount of tPA was less than that in the normal ears, whereas, the amount of Fibrin was greater in ears with AOM than that in normal ears. It indicates that fibrinolysis involved in the process of adhesion formation of AOM, which may acts as a key factor.

Fibrin↗

Comparative study of the clinical efficacy of two dosing regimens of flutamide.

PURPOSE: We performed a randomized trial to compare the efficacy and toxicity of a new dose of flutamide (500 mg QD) with the currently recommended dose (250 mg q8h) in the treatment of advanced prostate cancer. The primary endpoints were percent of patients having normalization of prostate specific antigen (PSA), time to normalization, and percent change from baseline. Secondary endpoints were quality of life and toxicity. PATIENTS: Altogether, 440 men aged 46 to 94 years (mean 71 years) with confirmed stage M(1) disease, documented PSA rise >0.2 ng/mL, ECOG status 0 to 2, no second neoplasm, no liver function tests > or = 1.5-fold normal values, and no previous treatment for metastatic disease were entered in the trial. RESULTS: The PSA normalized by week 12 in 71% of the patients receiving 500-mg dose and 75% of those receiving the standard dose. The percent change in PSA was 89% and 96%, respectively. The treatment groups were not significantly different with respect to the incidence of adverse events: 71% v 68% in the 500-mg and 250-mg arms, respectively (P = 0.337). CONCLUSIONS: When combined with castration, 500 mg of flutamide appears to be equally effective in lowering serum PSA and is not significantly more toxic than conventional dosing. The use of 500 mg QD instead of the standard 250 mg q8h would result in a cost savings of 30%.

Aged↗

[Effect of tsaoko-anemarrhenae decoction on intracerebral c-fos, c-jun mRNA expression in interrupting pentylentetrazol kindled epileptic rat model].

OBJECTIVE: To investigate the molecular biological mechanism of anti-epileptic effect of Tsaoko-Anemarrhenae decoction (TAD) on epileptic model rats. METHODS: The pentylenetetrazol (PTZ) induced epileptic Sprague-Dawley rats were selected as the animal model. The effects of TAD on the c-fos, c-jun gene expression in the rats' brain were observed by in situ hybridisation. RESULTS: The c-fos, c-jun gene expression was obviously increased, TAD could effectively block the gene expression of c-fos, c-jun, showing better antiepileptic effect. CONCLUSION: The mechanism of TAD anti-epileptic effect might be correlated to the decrease of c-fos, c-jun gene expression.

Animals↗

Inhibition of human liver cytochrome P-450 1A2 by the class IB antiarrhythmics mexiletine, lidocaine, and tocainide.

Mexiletine, lidocaine, and tocainide are class IB antiarrhythmic drugs that are used for the treatment of ventricular arrhythmias and are known to inhibit drug metabolism. The objectives of this study were to characterize the inhibitory effects of mexiletine, lidocaine, and tocainide on cytochrome P-450 1A2 (CYP1A2) activity in human liver microsomes and to evaluate their relative inhibitory potencies by using a molecular model of this P-450 isozyme. The inhibitory effect of mexiletine, lidocaine, and tocainide on cytochrome CYP1A2 in human liver microsomes was examined with methoxyresorufin O-demethylase activity as an index of the catalytic activity of this P-450 isozyme. The kinetic inhibition types and Ki values were determined by Lineweaver-Burk plots and Dixon plots, respectively. Molecular modeling was used to assess the interaction of these agents with the CYP1A2 active site. Methoxyresorufin O-demethylase activity was inhibited 67 +/- 8%, 20 +/- 5%, and 7 +/- 4% by 2 mM mexiletine, lidocaine, and tocainide, respectively. Mexiletine and lidocaine exhibited competitive inhibition with Ki values of 0.28 +/- 0.12 mM and 1.54 +/- 0.74 mM, respectively, whereas the inhibition type of tocainide could not be determined because of its weak potency. A charge interaction between mexiletine and the Asp313 side chain in the CYP1A2 active site was found, and varying degrees of hydrogen bond formation between these three compounds and the CYP1A2 active site were observed. The in vitro inhibitory potencies in human liver microsomes (mexiletine > lidocaine > tocainide) are consistent with the structural interactions found in a molecular model of the active site of CYP1A2.

Anti-Arrhythmia Agents↗

[The protective effects of ciliary neurotrophic factor on inner ear damage induced by intensive impulse noise].

OBJECTIVE: To evaluate the feasibility of using ciliary neurotrophic factor(CNTF) to treat intensive impulse noise-induced inner ear damage. METHODS: The guinea pigs were given either CNTF (CNTF group) or 0.9% sodium chloride (NS group) for 3 weeks after impulse noise exposure. The animals receiving neither medicine nor noise served as a control group. ABR threshold shifts, the cochlear AchE staining as well as the hair cell and spiral ganglion cell counting were carried out in three groups of animals. RESULTS: The numbers of damaged hair cells and spiral ganglion cells in the CNTF group was less than that in the NS group. AchE activity alteration was also less severe in the CNTF group. Similar to the morphological results, changes in the auditory function, represented by the ABR threshold shifts, was less in the CNTF group. CONCLUSION: CNTF can protect cochlear hair cells and spiral ganglion cells against intensive impulse noise exposure by decreasing degeneration and necrosis of the hair cells in some extent and expedite hearing recovery.

Animals↗

Inhibition of human cytochrome P450 1A2 by flavones: a molecular modeling study.

Cytochrome P450 1A2 metabolizes a number of important drugs, procarcinogens, and endogenous compounds. Several flavones, a class of phytochemicals consumed in the human diet, have been shown to differentially inhibit human P450 1A2-mediated methoxyresorufin demethylase. A molecular model of this P450 was constructed in order to elucidate the molecular basis of the P450-flavone interaction. Flavone and its 3,5,7-trihydroxy and 3,5,7-trimethoxy derivatives were docked into the active site to assess their mode of binding. The site is hydrophobic and includes several residues that hydrogen bond with substituents on the flavone nucleus. The binding interactions of these flavones in the modeled active side are consistent with their relative inhibitory potentials, namely 3,5,7-trihydroxylflavone > flavone > 3,5,7-trimethoxylflavone, toward P450 1A2-mediated methoxyresorufin demethylation.

Amino Acid Sequence↗

Inhibition of methoxyresorufin demethylase activity by flavonoids in human liver microsomes.

Flavonoids are a class of dietary phytochemicals with anticarcinogenic properties. A series of ten structurally related flavonoids were evaluated for their effect on methoxyresorufin O-demethylase (MROD) activity in human liver microsomes. All compounds inhibited this cytochrome P450 1A2 (CYP1A2) mediated activity. 3,5,7-Trihydoxyflavone (galangin) was the most potent inhibitor, followed by 3-hydroxyflavone and flavone. The relative inhibitory potency of flavonoids is related to their structures. The results suggest that flavonoids may modulate pharmacological and toxicological effects mediated by CYP1A2.

Adult↗

Effects of impulse noise on cortical response threshold and inner ear activity of succinic dehydrogenase and acetylcholinesterase in guinea pigs.

The effects of impulse noise (firecrackers at 170 dB SPL, 1, 10, 20 rounds) on auditory cortical response threshold (CRT) and activity of succinic dehydrogenase (SDH) and acetylcholinesterase (AchE) in the inner ear were studied in 37 guinea pigs. The results showed that extent of damage in the cochlea was related to amount of exposure to the noise. Exposure to 10 rounds resulted in temporal threshold shift (TTS); to 20 rounds the result was permanent threshold shift (PTS). For the period when TTS existed, inverse correlation was noticed between enzyme activity change and CRT shift. The correlation could not be established when PTS was induced. The results suggest that the pathomechanism of PTS was more complex than that of TTS. The significance of the results is discussed.

Acetylcholinesterase↗

Comparative inhibition of human cytochromes P450 1A1 and 1A2 by flavonoids.

Flavonoids are a class of dietary phytochemicals that modulate various biological activities. The effects of flavone and five hydroxylated derivatives on the methoxyresorufin O-demethylase activity catalyzed by cDNA-expressed human cytochromes P450 (CYP)1A1 and 1A2 were examined. Flavone was a less potent inhibitor of CYP1A1 (IC50 = 0.14 microM) than CYP1A2 (IC50 = 0.066 microM). Four hydroxylated flavone derivatives (3-hydroxy-, 5-hydroxy-, 7-hydroxy-, and 3,7-dihydroxyflavone) were also potent inhibitors of CYP1A1 (IC50 < 0.1 microM) and CYP1A2 (IC50 < 0.3 microM). For CYP1A1, 7-hydroxyflavone exhibited a competitive mode of inhibition, with a Ki value of 0.015 microM and 6-fold selectivity for CYP1A1 over CYP1A2. 3,5,7-Trihydroxyflavone (galangin) showed the highest potency toward CYP1A2. The inhibition by galangin of the methoxyresorufin O-demethylase activity of CYP1A2 was mixed-type, with a Ki value of 0.008 microM. Galangin showed 5-fold selectivity in its inhibition of CYP1A2 over CYP1A1. The results indicate that some flavonoids have high potencies and selectivities for inhibition of CYP1A isozymes. This may have important implications for cancer prevention, as well as other pharmacological and toxicological effects of these compounds.

Cell Line↗

Binding of beta-amyloid to the p75 neurotrophin receptor induces apoptosis. A possible mechanism for Alzheimer's disease.

Alzheimer's disease is a neurodegenerative disorder characterized by the extracellular deposition in the brain of aggregated beta-amyloid peptide, presumed to play a pathogenic role, and by preferential loss of neurons that express the 75-kD neurotrophin receptor (p75NTR). Using rat cortical neurons and NIH-3T3 cell line engineered to stably express p75NTR, we find that the beta-amyloid peptide specifically binds the p75NTR. Furthermore, 3T3 cells expressing p75NTR, but not wild-type control cells lacking the receptor, undergo apoptosis in the presence of aggregated beta-amyloid. Normal neural crest-derived melanocytes that express physiologic levels of p75NTR undergo apoptosis in the presence of aggregated beta-amyloid, but not in the presence of control peptide synthesized in reverse. These data imply that neuronal death in Alzheimer's disease is mediated, at least in part, by the interaction of beta-amyloid with p75NTR, and suggest new targets for therapeutic intervention.

3T3 Cells↗

The "toughening" phenomenon in rat's auditory organ.

In audiological "toughening" or "conditioning" phenomenon prior exposure to moderate noise reduces the extent of hearing deterioration caused by the subsequent exposure to traumatic test noise known to cause inner ear damage. "Toughening" has been demonstrated in many mammalian laboratory animals such as guinea pig and chinchilla but not in rat or mouse. Our aim was to study the occurrence of this phenomenon in the rat. Ninety-one white male Wistar rats were divided into four groups: unexposed control group (U, n = 10), "conditioning" only (C, n = 32), "conditioning" plus test noise (C + T, n = 36) and test noise only (T, n = 13). Groups C and C + T were "conditioned" for 10 hours with 4.0 kHz OBN between 55 and 95 dB sound pressure levels (SPLs). After 10 hours rest groups C + T and T were exposed to the same noise at 105 dB SPL for 13 hours. The hearing thresholds were determined by auditory brainstem response audiometry (ABR) either immediately after or 3 weeks after the exposures. After that the animals were sacrificed. The cochleas were removed and perilymphatically fixed and further processed for quantitative cytocochleograms. Both the temporary (TTS) and the permanent threshold shifts (PTS) were smaller in animals which had been "conditioned" prior exposure to traumatic noise. Yet only 95 dB SPL "conditioning" gave statistically significant difference (p < 0.05) in PTS. From our results we conclude that "conditioning" effect seems to be present also in the rat. However to confirm this, further experiments are needed. The mechanisms behind "conditioning" are still unknown and also to clarify them, further efforts are needed.

Acoustic Stimulation↗

Effect of hyperbaric oxygen treatment on permanent threshold shift in acoustic trauma among rats.

Impulse noise from firearms is a common cause of acute acoustic trauma (AAT). Recently hyperbaric oxygen treatment has become available in many hospitals treating AAT. We exposed 39 Wistar rats to intense impulse noise of 60 shots from the assault rifle (162 dB SPL). After the exposure 15 animals were given hyperbaric oxygen treatment (HBO) by 10 treatment cycles of 90 minutes 100% oxygen in 0.25 MPa, one treatment cycle per day. Four weeks after the exposure the hearing thresholds were measured with auditory brainstem response audiometry at frequencies of 1.0, 2.0, 4.0, 6.0, 8.0 and 10.0 kHz. Characteristics for the resulting noise-induced hearing loss were large variations in its severity not only between animals, but also between the ears of a single animal. The largest permanent threshold shifts were found at 6.0, 8.0 and 10.0 kHz. Most of the HBO-treated animals showed less threshold shift than the non-treated animals. The difference between the HBO group and the control group was only slightly statistically significant (p = 0.067).

Animals↗

[Treatment effects of fibroblast growth factors on blast-induced hearing loss].

Nineteen guinea pigs were chosen to measure the compound action potential (CAP) using the silver-ball electrode before and after explosion and 48 h after perfusion of acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF). After explosion the average CAP thresholds in the group perfused with bFGF and aFGF were 88.7 dB and 93.2 dB SPL respectivery, the CAP threshold in the control group was 119.4 dB SPL. The difference was significant. The results of the hair cell count from the surface preparation of the cochlea showed that hair cell damage in the control group was more severe than that in the group perfused with aFGF and bFGF. It suggests that aFGF and bFGF perfused to the cochlea may facilitate recovery processes of hearing loss and help to repair the hair cell following acoustic trauma.

Action Potentials↗

Nerve growth factor rescues pigment cells from ultraviolet-induced apoptosis by upregulating BCL-2 levels.

Apoptosis plays an important role in eliminating dysfunctional damaged cells. For skin, the best characterized injurious environmental agent is ultraviolet (UV) irradiation. Most of the damaging UV irradiation is absorbed in the epidermis and leads to apoptosis of keratinocytes. However, epidermal melanocytes appear to be protected from UV-induced apoptosis. We now report that in pure cultures melanocytic cells undergo characteristic apoptosis after physiologic UV exposures. However, nerve growth factor (NGF) supplementation protects them from this programmed cell death. Furthermore, we show that NGF protects melanocytic cells from UV-induced apoptosis by upregulating BCL-2 protein in these cells and that prior downregulation of BCL-2 abrogates the NGF protective effect on melanocytes. Our data suggest that NGF, known to be constitutively produced by epidermal keratinocytes and induced in these cells after UV irradiation, may preserve the population of cutaneous melanocytes that would otherwise be depleted by casual sun exposure.

Apoptosis↗

Relation between plasma and saliva concentrations of enoxacin, ciprofloxacin, and theophylline.

To assess the reliability of predicting plasma concentrations of enoxacin, ciprofloxacin, and theophylline from drug concentrations in saliva, six healthy volunteers received single oral doses of enoxacin, ciprofloxacin, and theophylline administered in combination on each of four separate study days, with different, doses separated by at least 5 days. Drug concentrations were determined by a newly developed high-performance liquid chromatography (HPLC) assay, which could measure simultaneously all three drugs in plasma or saliva. Saliva data from the postabsorptive phase after drug administration were used to minimize the effects of variation in absorption. There were good correlations between saliva and plasma concentrations of enoxacin, ciprofloxacin, and theophylline (r = 0.91, 0.88, and 0.98, respectively). The mean (+/-SD) saliva-to-plasma (S/P) ratio for theophylline was 0.63 +/- 0.06 with a coefficient of variation (CV) of 7.9 +/- 2.7%. In contrast, the S/P ratios and CV values for enoxacin and ciprofloxacin were 0.72 +/- 0.21 and 28.9 +/- 11.1%, and 0.58 +/- 0.15 and 25.3 +/- 6.7%, respectively. Because of the large inter- and intraindividual variability, saliva concentrations of enoxacin and ciprofloxacin are not reliable for predicting plasma concentrations. However, saliva may be used reliably for predicting plasma concentrations of theophylline.

Adult↗